The '''Library of Congress''' is the research library
that officially serves the United States Congress
, but which is the ''de facto'' national library
of the United States
. It is the oldest federal cultural institution in the United States. The Library is housed in three buildings on Capitol Hill
in Washington, D.C.
, and also maintains the National Audio-Visual Conservation Center|Packard Campus
in Culpeper, Virginia
, which houses the National Audio-Visual Conservation Center
The library is the List of largest libraries|second largest library by collection size
, with the largest being the British Library
. The Library's "collections are universal, not limited by subject, format, or national boundary, and include research materials from all parts of the world and in more than 450 languages. Two-thirds of the books it acquires each year are in languages other than English."